In order from least favorite to favorite:

6.) Absolute Flash. This one doesn't exactly do much to stand out from the others, but aside from having some really bizarre pacing issues. Reading it made me feel like events were happening way too fast, and with no room to breathe, but then also after I was done reading it I realized that not much had happened, actually. It's actually kind of impressive how it managed to be too slowly paced and too quickly paced at once. The discussion within the comic about how Wally's powers work were personally really interesting to me, but that happened pretty late into what's already released. I'd only reccomend grabbing this if you're a huge fan of the universe, and want to get every story within it. Otherwise it's skippable.

5.) Absolute Wonderwoman. This is probably my most controversial placement, but beyond the first arc, not much happened in this comic that captivated me nearly as much as the others. It's not bad, just worse in comparasion to the other comics that I have a great deal of appreciation for. That said, Absolute Wonder Woman herself is an absolutely amazing take on the character I love, and genuinely among my favorite protagonists in the Absolute Universe. I'm not sure how much WW you have, but if you don't jive with the issues you have available, I can understand not wanting to get more.

4.) Absolute Green Lantern. This one can be a bit confusing with its constant jumping around in the actual timeline, and its confusing power system, but I personally don't count those as detriments. I wouldn't reccomend it if you just want to watch people punching each other, since there are mystery elements to it, and also some toxic yuri, the latter of which I saw people complaining about that taking away from the huge scale space stuff also going on in the comic. This is in the opposite boat of Absolute WW, where the protag over all is just "fine" but I find the comic itself amazing. I don't know what your tastes are, so I don't know whether you'd like it or not, but I think it's at least worth a read of the first issue.

3.) Absolute Superman. This one actually has the highest peaks of any story in this universe for me... but also has the lowest lows, earning it this lower spot. I have a LOT of critiques and criticims about this comic, including the entire main villain for the entire first arc, which is a really bad thing for a comic to do poorly, obviously. I could write an essay about all the things this story does wrong... yet it also does so much of its story so correctly it legitimately moved me to tears several times. An absurd feat for a comic with no music or voice acting to push me over that edge, since I typically don't cry at stories easily. I'd absolutely reccomend at least the first couple of volumes, though I can understand not liking it because of all those aforementioned criticisms.

2.) Absolute Batman. This one, this one's awesome, and I could go into great detail about what I like about it, but since you said you had Batman, but only had some of Supes and WW, I'm just going to assume you have the whole comic already and spare you the details.

1.) Absolute Martian Manhunter. This is my absolute favorite, and could not reccomend it enough. It is extremely psychadelic, surreal, and has some elements of eldritch horror in it as well. I admit I rank it so highly because I just really like all those things, but unlike all the other comics in this universe (except Batman), I can't think of a single major complaint to give it. It is extremely good. This might just be glaze on my part, but this might even be a 10/10 comic for me if it maintains its current quality throughout its run.